The intra- and inter-assay variation of the indirect mixed antiglobulin reaction test: is a quality control suitable?

The test most commonly used to detect sperm antibodies is the mixed antiglobulin reaction (MAR), standardized by the World Health Organization. The indirect MAR test detects soluble sperm antibodies in seminal plasma by using healthy donor spermatozoa as antigen. In this study we systematically investigated the influence of donor spermatozoa and the source of sperm antibodies upon the results of the indirect MAR test, and calculated the intra- and inter-assay variations. Using one individual seminal plasma and the same donor semen, results of the indirect MAR test are highly reproducible (low intra-assay variation). Two dimensions of inter-assay variation must be considered: (i) serial ejaculates of an individual donor may be used at different times; (ii) different donors may be applied to identical antibody sources. Donor spermatozoa strongly influenced the results of the indirect MAR test. Using multivariate statistical tests, highly significant main effects between the different donors (P < 0.001) and specific reciprocal effects between donor spermatozoa and seminal plasma samples (P < 0.001) were observed. The high inter-assay variation of the indirect MAR test will lead to incorrect results. There is urgent need of a reliable and reproducible test for sperm antibody detection to improve quality control of the methods.